Solid-state lighting devices such as light emitting diodes (LEDs) may transmit ultraviolet (UV) light for curing photo sensitive media such as coatings, including inks, adhesives, preservatives, etc. Curing time of these photo sensitive media may be controlled via adjusting intensity of light directed at the photo sensitive media from the solid-state lighting device. The light intensity may be adjusted by increasing current flow to the solid-state lighting devices. However, as the power supplied to the solid-state lighting devices increases, the thermal output from the solid-state lighting devices also increases. If heat is not transferred away from the solid-state devices, their performance may degrade. One way to transfer heat away from a solid-state device is to transfer heat from the solid-state device to a liquid medium. For example, LEDs may be mounted to one side of a heat sink that includes a channel that holds a liquid medium. The liquid flows through the heat sink and transfers heat away from the heat sink and the LEDs to a remote area where the heat may be extracted from the liquid medium. Such a cooling system may remove a desired amount of heat from LEDs during most conditions. Nevertheless, if coolant flow becomes restricted or reduced, LEDs operation may degrade.
The inventor herein has recognized the above-mentioned issues and has developed a method for operating a plurality of light emitting devices, comprising: supplying an electrical current to the plurality of light emitting devices; and stopping flow of the electrical current in response to a rate of temperature increase of the plurality of light emitting devices exceeding a threshold rate of temperature increase.
By controlling current flow through a plurality of light emitting devices in response to a rate of temperature increase of the plurality of light emitting devices, it may be possible to shutdown operation of the plurality of light emitting devices before one or more of the plurality of light emitting devices experiences thermal degradation. For example, a temperature sensing device may be in thermal communication with a heat sink. Light emitting devices may be coupled to the heat sink so that heat is transferred from the light emitting devices to the heat sink. The heat sink temperature may be indicative of light emitting device temperature. If the heat sink temperature increases at a rate that is greater than a threshold rate of temperature increase, electrical current flowing to the light emitting devices may be stopped to reduce the possibility of the light emitting devices degrading.
The present description may provide several advantages. In particular, the approach may provide improved temperature control response. Further, the approach may be useful for reducing the possibility of light emitting device degradation. Further still, the approach may be applied to a system that monitors one or more light emitting device via one or more temperature sensing devices.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.